Modulation of charge migration and ink flow dynamics exceeding 19% efficiency for blade-coating pseudo-planar heterojunction organic solar cells

Abstract

Constructing efficient and regular charge transport channels is essential to achieve high power conversion efficiency (PCE) in pseudo-planar heterojunction (PPHJ) organic solar cells (OSCs). Nanoimprint lithography (NIL) has been proven to be an effective strategy in promoting exciton dissociation and charge transport for PPHJ devices fabricated by a sequential spin-coating deposition method. However, the precise regulation of active layer ink inter-permeation during sequential blade-coating (SBC) and an augmented exciton dissociation interface to increase carrier separation/transport efficiency remains challenging. Here, we have for the first time applied an NIL-assisted SBC technique to fabricate high-performance PPHJ OSCs. A blade-coated donor with subsequent NIL treatment can induce ordered molecular stacking and increase crystallinity to inhibit donor film erosion from the acceptor solution. Besides, the micropattern will affect acceptor ink flow during blade-coating, which can precisely control donor/acceptor inter-penetration to enlarge the exciton dissociation interface and form regular charge migration channels. Consequently, the champion PPHJ device via an NIL-assisted SBC technique with a suitable micropattern exhibits the highest PCE of 19.14% for a PM6/BO-4Cl:L8-BO system. Furthermore, the 1.00 cm² ternary device exhibits a competitive PCE of 17.98%. This charge migration strategy provides a path for constructing desirable active layer morphology with ideal vertical gradient distribution and regular charge transport pathways to achieve large-area high-performance PPHJ OSCs.